Comparison of four inverse modelling systems applied to the estimation of HFC-125, HFC-134a, and SF<sub>6</sub> emissions over Europe

Abstract

Abstract. Hydrofluorocarbons (HFCs) are used in a range of industrial applications and have largely replaced previously used gases (CFCs and HCFCs). HFCs are not ozonedepleting but have large global warming potentials and are, therefore, reported to the United Nations Framework Convention on Climate Change (UNFCCC). Here, we use four independent inverse models to estimate European emissions of the two HFCs contributing the most to global warming (HFC-134a and HFC-125) and of SF 6 for the year 2011. Using an ensemble of inverse models offers the possibility to better understand systematic uncertainties in inversions. All systems relied on the same measurement time series from Jungfraujoch (Switzerland), Mace Head (Ireland), and Monte Cimone (Italy) and the same a priori estimates of the emissions, but differed in terms of the Lagrangian transport model (FLEXPART, NAME), inversion method (Bayesian, extended Kalman filter), treatment of baseline mole fractions, spatial gridding, and a priori uncertainties. The model systems were compared with respect to the ability to reproduce the measurement time series, the spatial distribution of the posterior emissions, uncertainty reductions, and total emissions estimated for selected countries. All systems were able to reproduce the measurement time series very well, with prior correlations between 0.5 and 0.9 and posterior correlations being higher by 0.05 to 0.1. For HFC-125, all models estimated higher emissions from Spain + Portugal than reported to UNFCCC (median higher by 390 %) though with a large scatter between individual estimates. Estimates for Germany (+140 %) and Ireland (+850 %) were also considerably higher than UNFCCC, whereas the estimates for France and the UK were consistent with the national reports. In contrast to HFC-125, HFC-134a emissions from Spain + Portugal were broadly consistent with UNFCCC, and emissions from Germany were only 30 % higher. The data suggest that the UK over-reports its HFC-134a emissions to UNFCCC, as the model median emission was significantly lower, by 50 %. An overestimation of both HFC-125 and HFC-134a emissions by about a factor of 2 was also found for a group of eastern European countries (Czech Republic + Poland + Slovakia), though with less confidence since the measurement network has a low sensitivity to these countries. Consistent with UNFCCC, the models identified Germany as the highest national emitter of SF 6 in Europe, and the model median emission was only 1 % lower than the UNFCCC numbers. In contrast, the model median emissions were 2-3 times higher than UNFCCC numbers for Italy, France, and Spain + Portugal. The country-aggregated emissions from the different models often did not overlap within the range of the analytical uncertainties formally given by the inversion systems, suggesting that parametric and structuralPublished by Copernicus Publications on behalf of the European Geosciences Union. Comparison of four inverse modelling systems applied to the estimation of emissions uncertainties are often dominant ...

Abundance and Sources of Atmospheric Halocarbons in the Eastern Mediterranean

“…The differences between the country-wide emissions reported to UNFCCC and the range of results found in this study seem to be somewhat more 665 pronounced than in previous studies. This is consistent with Brunner et al [2016], who reported a relatively large range of regional emission estimates depending on the employed inverse modelling system.…”

“…Europe resemble the results of other studies performed for earlier years [Lunt, et al, 2015;Brunner, et al, 2016;Say, et al, 2016]. The differences between the country-wide emissions reported to UNFCCC and the range of results found in this study seem to be somewhat more 665 pronounced than in previous studies.…”

Recent increases in the atmospheric growth rate and emissions of HFC-23 (CHF<sub>3</sub>) and the link to HCFC-22 (CHClF<sub>2</sub>) production

“…The details of the inversion method were recently published in estimating Swiss methane emissions . This inversion methodology was part of an HFC inversion intercomparison (Brunner et al, 2017) and was applied to HFC and HCFC emissions in the eastern Mediterranean (Schö-nenberger et al, 2017). Here, the inversion relies on the continuous observations from the Jungfraujoch and Mace Head and requires a priori estimates of the emissions distribution.…”

Abundance and sources of atmospheric halocarbons in the Eastern Mediterranean

“…Whereas only chlorinated and brominated halocarbons are responsible for stratospheric ozone depletion, most long-lived halocarbons are potent greenhouse gases (Carpenter et al, 2014;Farman et al, 1985;Molina and Rowland, 1974;Myhre et al, 2013).…”

“…The combination of observations with simplified global-scale box models allows the independent derivation of global emissions (e.g., Carpenter et al, 2014;Rigby et al, 2010;Vollmer et al, 2015). The application of more detailed atmospheric models has proven to be a powerful tool to quantify emissions on a spatially and temporally more explicit level enabling for emission estimates on a continental to country scale Ganesan et al, 2014;Graziosi et al, 2015;Hu et al, 2015;Keller et al, 2012;Kim et al, 2010;Lunt et al, 2015;Maione et al, 2014;e.g., Manning et al, 2003;Saikawa et al, 2012;Stohl et al, 2009).…”